#!/bin/sh /etc/rc.common

START=15

ram_size()
{
	local line

	while read line; do case "$line" in MemTotal:*) set $line; echo "$2"; break ;; esac; done </proc/meminfo
}

zram_size()	# in megabytes
{
	local zram_size="$( uci -q get system.@system[0].zram_size_mb )"
	local ram_size="$( ram_size )"

	if [ -z "$zram_size" ]; then
		# e.g. 6mb for 16mb-routers or 61mb for 128mb-routers
		echo $(( ram_size / 2048 ))
	else
		echo "$zram_size"
	fi
}

zram_applicable()
{
	local zram_dev="$1"

	grep -sq ^"$zram_dev " /proc/swaps && {
		logger -s -t zram_applicable -p daemon.notice "[OK] '$zram_dev' already active"
		return 1
	}

	[ -e "$zram_dev" ] || {
		logger -s -t zram_applicable -p daemon.crit "[ERROR] device '$zram_dev' not found"
		return 1
	}

	which mkswap >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'mkswap' not installed"
		return 1
	}

	which swapon >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapon' not installed"
		return 1
	}

	which swapoff >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapoff' not installed"
		return 1
	}
}

zram_dev()
{
	local core="$1"

	echo "/dev/zram${core:-0}"
}

zram_reset()
{
	local dev="$1"
	local message="$2"
	local proc_entry="/sys/block/$( basename "$dev" )/reset"

	logger -s -t zram_reset -p daemon.debug "$message via $proc_entry"
	echo "1" >"$proc_entry"
}

zram_comp_algo()
{
	local dev="$1"
	local zram_comp_algo="$( uci -q get system.@system[0].zram_comp_algo )"

	if [ -z "$zram_comp_algo" ] || [ ! -e /sys/block/$( basename $dev )/comp_algorithm ]; then
		return 0
	fi

	if [ `grep -c "$zram_comp_algo" /sys/block/$( basename $dev )/comp_algorithm` -ne 0 ]; then
		logger -s -t zram_comp_algo -p daemon.debug "Set compression algorithm '$zram_comp_algo' for zram '$dev'"
		echo $zram_comp_algo > "/sys/block/$( basename $dev )/comp_algorithm"
	else
		logger -s -t zram_comp_algo -p daemon.debug "Compression algorithm '$zram_comp_algo' is not supported for '$dev'"
	fi
}

list_cpu_idx()
{
	# Offset by 1 if /dev/zram0 is in use by /tmp
	if mount | grep -q /dev/zram0; then
		local line i=1
		# Hot-add new ZRAM device (if necessary)
		if [ ! -b /dev/zram1 ]; then
			cat /sys/class/zram-control/hot_add
		fi
	else
		local line i=0
	fi

	while read line; do {
		case "$line" in
			[Pp]rocessor*)
				echo $i
				i=$(( i + 1 ))
			;;
		esac
	} done <"/proc/cpuinfo"
}

start()
{
	# http://shmilyxbq-compcache.googlecode.com/hg/README
	# if >1 cpu_core, reinit kmodule with e.g. num_devices=4

	local zram_size="$( zram_size )"
	local zram_dev core

	for core in $( list_cpu_idx ); do {
		zram_dev="$( zram_dev "$core" )"
		zram_applicable "$zram_dev" || return 1

		logger -s -t zram_start -p daemon.debug "activating '$zram_dev' for swapping ($zram_size MegaBytes)"

		zram_reset "$zram_dev" "enforcing defaults"
		echo $(( zram_size * 1024 * 1024 )) >"/sys/block/$( basename "$zram_dev" )/disksize"
		zram_comp_algo "$zram_dev"
		mkswap "$zram_dev"
		swapon "$zram_dev"
	} done
}

stop()
{
	local zram_dev proc_entry

	for core in $( list_cpu_idx ); do {
		zram_dev="$( zram_dev "$core" )"
		proc_entry="/sys/block/$( basename "$zram_dev" )/reset"

		grep -sq ^"$zram_dev " /proc/swaps && {
			logger -s -t zram_stop -p daemon.debug "deactivate swap $zram_dev"
			swapoff "$zram_dev"
		}

		zram_reset "$zram_dev" "claiming memory back"
	} done
}